Suggest Remedies For Delayed Periods In Spite Of Taking Birth Control

I am very worried because that I had unprotected sex with my girl friend four time in a month and gave her unwanted 72 all the time .and as of now her period date was on 5 august and till now period not happened till 11 august .and pregnancy test is also negative. What to do pls suggest..I am very worried and tensed...pls help.?